The so-named guillotine shearing machine is a well-known tool. One blade, generally the upper one, is mobile and slides on runners which keep the movement rectilinear and transversal to the cutting plane. The blade is operated by cams or by hydraulic systems. Shearing machines used for cutting lengths of sheet metal, profiles, continuous moving bands, comprise a pair of drums between which the band passes, and radially set blades which meet at the shearing plane to cut through the moving piece.
The radial position of the blades obviously determines the angle they assume, which angle varies progressively during cutting. This means that the advantages of speed and simplicity in continuously cutting a moving band are to some extent adversely affected and the operation lacks that precision which can only be obtained with blades set perfectly perpendicular to the piece to be cut. The invention here described avoids these drawbacks at the same time offering considerable advantages as will now be explained.